New York: Worried about what your dog is chewing on when you're at work, or whether your home is secure while on vacation? New apps can transform old smartphones into remote security cameras for home monitoring systems.

Presence, the application which was launched late last month, converts a spare Internet-connected iPhone, iPad or iPod Touch into a free video camera with real-time video and audio streaming, and motion detection.

"Essentially we give you an inexpensive security system that you can use to monitor your house, or help you watch your kids, cats, elderly relatives or act as a baby or nanny cam," said Gene Wang, Chief Executive of the California-based company People Power.

Unlike traditional monitoring systems that are expensive and need technical knowledge to install and use, Presence is a free do-it-yourself system that can be set up simply by downloading and configuring the app.

The app can help to avoid false alarms, because it sends a video clip in an email to the user showing the motion that triggered the alert, Wang said.

He added that many people have replaced their old smartphones with new ones and a monitoring system would be a good way to make use of the old devices.

Another app created by a company called People Power 1.0 for iPhone and Android reads electricity meters in real time to show consumers how much they're spending and whether they are going over budget.